With composite and s-video, the 990 will output the menu on top of the video signal, both the setup menu and assorted "pop-up" messages (volume setting, etc.).

With component, the 990 will output the setup menu only, and it will replace the video signal with a black screen at 480i as a backdrop for the menu.

With DVI, the 990 does "pure" switching - no video signal manipulation at all, including menu generation.
Glad to hear that you got it working...

You are looking to the HD Fury to let you use the HDMI out of your DVR and thus free up the component out for the secondary display, because the display lacks DVI or HDMI, correct? Here are my big concerns, one comping from my experience with HD cable boxes (not HD satellite boxes) and the other from a video switching quandary.

No, what I was originally thinking was using the component output of the 990 for the LCD. I now know this won't work.

but it appears that if you have it operating in "Single Mode" the "TV2" outputs will always be active and will get the same signal as the HD "TV1" output (with HD stations scaled down to 480i)

I actually have it operating in dual mode. The SD TV upstairs is also run from this same box. So, that wouldn't work either.